Water treatment system with retrievable mounting frame assembly for diffusors

ABSTRACT

A method for aerating water in a treatment basin includes positioning at least one bridge above an upper surface of the water in the basin; providing a retrievable mounting frame assembly; securing a guide rail assembly to the bridge; transporting the mounting frame assembly on a transport device to a selected position on the walkway near the guide rail assembly; securing a transfer crane to the walkway proximate the guide rail assembly; transferring the mounting frame assembly from the transport device for connection to the a one guide rail assembly; connecting the mounting frame assembly to the guide rail assembly to provide a supply of air to the first air distribution conduit; moving the retrievable mounting frame assembly from a first position above the upper surface of the water to a second position below the water; and initiating a flow of air to the first air distribution conduit.

PRIORITY APPLICATION

This application claims the benefit of priority to and is a divisionalapplication of U.S. application Ser. No. 16/593,870 filed Oct. 4, 2019,entitled “Water Treatment System With Retrievable Mounting FrameAssembly For Diffusors,” the entire contents of which are herebyexpressly incorporated herein by this reference including, withoutlimitation, the specification, claims, and abstract, as well as anyfigures, tables or drawings thereof.

FIELD OF THE INVENTION

The present invention relates generally to wastewater treatment, andmore particularly, to retrievable aeration systems utilized in thegasification of liquids of water in wastewater treatment basins.

BACKGROUND OF THE INVENTION

Activated sludge systems are used to break down organic solids inwastewater by aerobic digestion from microorganisms (biomass). Theorganisms are then recycled and the remaining products are treated waterand waste solids. Carbonaceous Biochemical Oxygen Demand (CBOD) is theamount of carbon-based organic matter in the water that isbiodegradable. It is measured as Biochemical Oxygen Demand (BOD). Sincethis organic matter or nutrients deplete oxygen in the water bydigestion of aerobic nutrients by microbes, the goal is to remove theorganic solids in the water and lower the BOD level. This is also knownas BOD removal. The level of BOD is controlled so that the finaldecanted water can be released into streams or rivers.

The basic equation for treating BOD with the activated sludge process isBOD+O₂+Bacteria→CO₂+H₂O (BOD+Oxygen→Carbon Dioxide+Water).

Since the microorganisms use oxygen to break down the suspended solids(SS), oxygen must be introduced into the mixture of water and solids.This mixture is called Mixed Liquor Suspended Solids (MLSS). The amountof oxygen must be great enough for the biomass to break down the solidsin the resident time in the waste tank. In order to maximize the amountof oxygen that is dissolved in the water (DO), the oxygen transferefficiency (OTE) is examined. The more oxygen, the better the biomasscan feed and maintain the proper biomass to solids ratio (F:M). Theorganisms and solids form into an aggregate called floc.

Biological nutrient removal is also a part of the activated sludgeprocess, since nitrogen and phosphorus are elements which can promotethe growth of noxious algae in surface waters that received treatedwaste water. Another demand of oxygen in an activated sludge process iscreated by oxidizing ammonia to nitrates (nitrification).

A general formula is:

NO³—→NO²—→NO→N²O→N₂ gas

Various types of water-treatment apparatus have been developed and areused, for example, in clarification plants/waste water-processingaerobic digestion tanks. In a typical system, a plurality of aerationelements is disposed on a distribution conduit, whereby the distributionconduit on the one hand serves for the supply of air or gas to theaeration elements, and on the other hand also serves for the securementof the aeration elements. A plurality of distribution conduits can inturn be combined to form a system.

In known systems, tube-, disc-, and/or strip-type diffusor elements aregenerally fixed to the bottom of a water treatment tank or to the bottomsurface of a treatment pond via specialized brackets or areself-weighted so that the aeration elements remain at the bottom of thetreatment tank or pond to be treated. Aeration elements are typicallyarranged in various types of grid configurations or in zones on thebottom of the water tank or pond to be treated. Aeration elements in theform of diffusors strips, tubes, or discs, as are commonly used, areconsumable in the activated sludge process, and therefore are subject toa great deal of wear and tear, in that the membrane or other materialthat surrounds the frame or body of the diffusor element can be damagedby movement of the water around the elements. Such aeration elements,therefore, are routinely replaced every 6 to 10 years. The diffusorelement frame/body itself can become clogged with debris or even warpedover time, or the clamp, bracket, or other element that secures theaeration element to the tank floor can become worn or damaged andrequire replacement or repair. Maintenance of the diffusor elements,therefore, can be difficult, expensive, and time-consuming, since anydamaged components must be accessed and replaced within the water tankor pond, as the diffusor elements are secured to the bottom of the tankvia clamps, brackets, or other securement means, as noted above.

As noted above, typically strip-like or tube-like aeration elements alsoare secured in place to the floor or bottom of a tank or water to betreated, for example, by means of an assembly bracket or otherattachment means. These types of arrangements are known as fixed griddiffusor systems. By way of illustration, with one type of assemblybracket, cooperating upper and lower profiled portions are securedaround the aeration element at opposite ends of each element. Theassembly bracket is in turn secured to the floor by either an anchorbolt in the center bottom hole directly into the tank floor or by twoheight-adjustable anchors through the two outer holes to enable levelingof the diffuser to bottom of the tank for maintaining the position of anaeration element. It is contemplated that a plurality of brackets can beutilized along the length of the aeration element, rather than only onits ends.

A disadvantage associated with these types of fixed grid systems inwastewater treatment system operations, however, relates to maintenanceof the aeration elements once in place and operating in the water basin.To install, repair, replace, or otherwise access the fixed grid-typediffusor system, the water basin must be drained. Thus, in a wastewatertreatment plant, the aeration basin must be shut down completely at thispoint, interrupting processing, unless the system includes a second tankor basin that can still be operated while the first tank is not in use.

A retrievable and modular system, therefore, offers built-in redundancy,that is, 100% uptime, as the basin and the entire aeration system mustnot be taken out of service during repair and maintenance operations,thus offering much lower costs with regard to operation and maintenance.

While retrievable aeration systems have been developed for use in watertreatment systems, most current systems are wall mounted; that is theaeration element frame works in cooperation with a mounting system thatis fixed to the wall of a tank, thus limiting the availableconfigurations of the aeration element racks to distances near the tankor basin walls. A basin width that is greater than or equal to 12.5 m,or 40 feet, for example, generally limit whether a retrievable or fixedgrid system can be used. Further, elongated aeration basins sharingcommon walls have limitations regarding the feasibility of retrievablesystems for a reasonable investment cost.

The retrievable diffusor frame based on a bridge-mounted systemaccording to the present application therefore overcomes the limitationsof a wall-mounted system by spanning across the tank, in the event thegeometry of the tank does not provide for a sufficient number ofdiffusor frames or diffuser coverage on the bottom of the tank or forair distribution in the center of the tank. The system furthereliminates the need for parallel or redundant tank systems.

The system of the present application further facilitates replacementand maintenance operations for the diffusors and frames by providing atransfer system including transport device for the diffusor frames orracks and transferrable crane that enables the frames and diffusors tobe moved along the bridge into position for deployment or removal atselected positions along the length of the bridge.

Thus, according to the present invention, rather than securing theaeration elements to the tank or pond floor via clamping bracket orother means in a fixed-grid type of system, the aeration elements aresecured onto a retrievable mounting frame or rack that can be loweredinto or raised out of the tank via a guide rail system that is securedto a bridge spanning the tank. Further, unlike known retrievablediffusors used in water treatment which are commonly mounted to the wallof the tank or basin, the system assembly according to the presentapplication instead allows access to the entire contents of the tank orbasis by providing a bridge-mounted system that can be configureddepending on the geometry and dimensions of the tank or basin. Thesystem increases operating efficiency by eliminating downtime involvedwith draining the tank when repair or maintenance to the system isrequired.

As noted above, the system according to the present invention allowsdeployment of more retrievable aeration elements per tank, compared tosolely wall mounted systems, thereby overcoming tank width and/ordiameter limitation of rectangular or round tanks. The system thereforeprovides for a greater aeration capacity using retrievable diffuserscompared to round tanks. The width/diameter limitation of solely wallmounted retrievable system is approximately 60 ft (18.25 m).

SUMMARY OF THE INVENTION

Embodiments of the present invention address the above-noteddisadvantages by providing a novel wastewater treatment system with abridge-mounted, retrievable aeration system.

Aspects of the invention are directed to a water treatment system foruse in a water treatment basin with a bridge assembly extending betweenwalls of the tank and a retrievable aeration assembly with a guide railsystem fixed to the bridge for deploying and retrieving the diffusorframe assembly. The system further includes a transport system formoving and deploying the diffusor assemblies that includes a transportdevice for moving the frame assemblies along the length of the bridgeand a transferrable crane moveable between lifting positions along thebridge for moving the frame assemblies between the guide rail system andthe transfer device. By providing a bridge system that spans the tankand is situated above the surface of the water and a retrievableaeration element frame assembly that can be deployed from selectedpositions on the bridge system, the aeration elements and frames can bereplaced or maintained when necessary, without draining the water fromthe tank and without requiring a second tank for redundancy.

Aspects of the present invention is a water treatment system thatincludes at least one bridge assembly that spans a water treatment tank;at least one retrievable diffusor frame assembly for diffuser elementsthat is moveable between a raised and lowered position into and out ofthe water tank; at least one guide rail system fixed to the bridgeassembly for moving the frame assembly between a first position abovethe surface of the water to a second position on a bottom surface of thetank; a transfer device for moving the frame assemblies along the lengthof the bridge; and a transferable crane moveable between liftingpositions along the bridge. The bridge walkway can include integratedguide tracks for accommodating wheels or castors of both the transferdevice and transferrable crane. In this connection, the crane caninclude a base that can be fixed to the bridge or walkway when the craneis in use to move the rack assemblies. Further, to facilitate movementof the crane along the bridge, the crane base can be provided withwheels and/or castors that cooperate with the tracks on the bridge thatare also used by the wheels or castors of the transport device, so thatthe crane assembly can be moved along the bridge or walkway, and thenfixed into lifting position for moving the frame assemblies.

Additional aspects of the invention are directed to a method fortreating wastewater in a treatment basin or tank. At least one bridge isinstalled that spans the basin and a plurality of retrievable aerationsystems, or guide rail system, are installed at selected positions alongthe length of the bridge. A transport system is provided that includes atransport device or cart for moving the diffusor frames along the bridgewalkway in guide tracks provided in the walkway to the guide rail systemand a transferrable crane for moving the diffusor frames between thetransport cart and the guide rail system.

Further specific features of the invention will be described in detailsubsequently.

BRIEF DESCRIPTION OF THE DRAWINGS

This object, and other objects and advantages of the present invention,will appear more clearly from the following specification in conjunctionwith the accompanying schematic drawings, in which:

FIG. 1A shows an isometric view of the water treatment system accordingto the present invention;

FIG. 1B shows an isometric view of the water treatment system with arectangular tank configuration with at least two bridge assemblies;

FIG. 1C shows a further isometric view of the system of FIG. 1;

FIG. 2A shows a view of the retrievable aeration system with verticalrail guides and frame assembly of FIG. 1C;

FIG. 2B shows an end elevation view of the bridge with vertical railguides, frame assembly, and cart of FIG. 2A;

FIG. 3A shows an end elevation view of the bridge assembly, transportcart, retrievable mounting frame assemblies, and a lifting and transfercrane fixed to the bridge assembly for moving and positioning theretrievable mounting frame assemblies;

FIG. 3B shows a perspective view of the lifting and transfer crane witha retrievable mounting frame assembly;

FIGS. 4A and 4B show detail views of the vertical guide rails and guiderails with mounting frame assembly, respectively;

FIGS. 5A-5D show detail views of the retrievable mounting frame assemblywith mounting brackets and aeration elements;

FIG. 6A shows a front view of a portion of the bridge with the portablecart and crane assembly positioned thereon;

FIG. 6B shows a top view of the bridge assembly, a transfer cart withmounting frame assembly on the bridge, and a mounting frame assembly ina lowered position;

FIG. 7 shows a further view of the bridge assembly with a diffuser racktransfer cart supporting a mounting frame assembly;

FIGS. 8A-9B show perspective views of the transferrable crane on thebridge walkway;

FIGS. 10A-10B show perspective views of the transfer crane of FIGS.9A-10B lifting a mounting frame assembly;

FIGS. 11A-11B show the mounting frame assembly in position on thetransfer cart after placement on the cart by the crane;

FIGS. 12A-12E show views of the transferrable crane, transfer trolley,and crane mounting base;

FIG. 13 shows a view of the mounting frame assembly in place on thetransfer cart; and

FIG. 14 shows the transfer station at an end of the bridge assembly forlifting and transferring the diffuser frame assemblies from or onto thebridge.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the drawings in detail, as shown in FIGS. 1A and 1C,the water treatment system 10 includes at least one bridge 2, aretrievable aeration system 200 including at least one retrievablemounting frame assembly 6 and a vertical guide rail system 19, atransferrable crane or lifting device 8, and a moveable transfer device,or cart 58 for moving the frame assembly along the bridge 2 intoposition for deployment of the frame assembly and aeration elements intoa water treatment tank 14. The water treatment system 10 is shown inFIG. 1A is contemplated for use in a water treatment tank 14, so thatthe bridge 2 extends across the water treatment tank 14, allowingworkers access to the mounting frame assemblies and crane or liftingdevice 8 through transfers stations 22 on at least one end of the bridgeassembly 2, as will be described below. The water treatment systemtherefore eliminates the need for the retrievable aeration system to bemounted only to the walls of the tank, but instead allows the mountingframe with aeration elements mounted thereon to be placed in a varietyof configurations in the water tank, thereby providing more efficientaeration and treatment of the water throughout the entire tank andavoiding draining of the tank for maintenance or repairs.

As noted above, the system according to the present invention allowsdeployment of more retrievable aeration elements per tank, compared tosolely wall mounted systems, thereby overcoming tank width and/ordiameter limitation of rectangular or round tanks. The system thereforeprovides for a greater aeration capacity using retrievable diffuserscompared to round tanks. The width/diameter limitation of solely wallmounted retrievable system is approximately 60 ft (18.25 m).

The bridge 2 preferably is constructed of steel and includes a pluralityof supports 16, each with a stabilizing base 18 secured to the typicallyconcrete floor 3 of the tank 14. The bridge 2 further includes awalkway, or catwalk, 20 extending across the length of the bridge 2. Atleast one guide track, preferably two guide tracks 21 positionedparallel to one another, are provided that run the length of the walkway20 for facilitating movement of the cart 58 and crane 8 along thewalkway 20 using wheels or castors on the cart 58 and crane 8,respectively, as will be described below with reference to FIGS. 2a and12a , for example. That is, the crane 8 and transfer cart 58 preferablycan run on the same track system. The bridge assembly further includestransfer stations 22, which are positioned at opposites ends of thewalkway and externally to the walls of the tank 14, so that systemoperators may access the bridge assembly 2 via the transfer stations 22and load and unload the components of the mounting frame assembly 6,cart 58, and crane 8 for use on the walkway 20. (See also FIG. 15,described below).

As shown in FIG. 1B, one or more bridges 2 may be used, depending on thesize and geometry of the water basin. For example, as shown in FIG. 1B,the system allows the use of more than one bridge 2 that span the entiretank 14 and to accommodate a variety of basin configurations, such asthe rectangular tank 14 shown in FIG. 1B. While FIG. 1B shows the use oftwo bridges 2 in a rectangular tank 14, it can be appreciated that thesystem of the present invention can be utilized in any tankconfiguration with any number of bridges in any contemplatedconfiguration, depending on the tank geometry.

As shown in FIGS. 1C, 2A-2B, and 4A-4B, the retrievable aeration system200 includes a vertical guide rail assembly 19, mounting frame assembly6 with a mounting frame 12, and a plurality of aeration elements 15mounted to the frame 12 via brackets 17 (see also FIGS. 5A-5D, describedbelow). The vertical guide rail assembly 19 serves for transferring theframe assembly 6 between a position above the water's surface and to aposition on the floor 3 of the tank 14. The vertical guide rail assembly19 includes preferably two vertical guide rails 34, 36 positionedparallel to one another and extending from the bridge 2 to the floor 3of the tank 14, a lower fixing bracket 38 for securing the verticalguide rail assembly 19 to the floor 3 of the tank 14, and an upperfixing bracket 40 for securing the vertical guide rail assembly 19 to arailing or other component of the bridge system 2. A flexible hose 52provides a supply of air to an air distribution conduit 29 and ispositioned between the vertical guide rails 34, 36 for connection via asuitable valve coupling to a flexible air supply hose 52. A first end 42of the control arm 25 is secured to air distribution conduit 29 and atan oppositely disposed second end 44 of the control arm 25 is attachedproximate an end of the central air distribution conduit 27 in themounting frame 12.

A hold-down bracket or rod 37 is provided between the vertical guiderails 34, 36, and is coupled to the air distribution line 22 andoperates to prevent the diffuser rack from rising up by its own systembuoyancy during standard operation. Guide brackets 90, which are fixedto hold-down rod 37, slidingly engage around guide rails 34, 36,respectively, to facilitate movement of the hold-down rod 37. Apneumatic or hydraulic source or jack system positioned on the walkway20, when actuated, causes the hold-down rod 37 and air distributionconduit 29 to be pushed vertically downward between and along thevertical guide rails 34, 36 via the guide brackets 90, thereby loweringthe mounting frame 12 and aeration elements 15 into the tank and waterfor placement on floor of the tank 14, as shown in FIG. 2A. The verticalguide rails 34, 36, being both secured to the floor of the tank 14 andthe bridge 2 or walkway 20, therefore provide a stabilizing support forthe hold-down bracket or rod 37 and air distribution conduit 29, withoutthe necessity of securing the guide rails or other support structure tothe walls of the tank.

It is also contemplated, however, that the vertical guide rail system 19could be mounted and secured to the walls of a water treatment tank foruse with the mounting frame assembly 6, without requiring the bridgeassembly 2 and walkway 20.

As shown in FIGS. 5A-5D, the mounting frame 12 includes at least twomounting rails 24, 26 arranged parallel and spaced from one another. Aplurality of aeration elements 15 are positioned on the mounting frame12, such that each of the two mounting rails 24, 26 is positionedproximate to opposite ends of the aeration elements 15. While thefigures show elongated aeration elements having an oval cross section,it is also contemplated that tubular or disc-shaped, or other aerationelements could be used with the frame assembly 6 and water treatmentsystem 10 according to the present invention with the same effect.

At least two further mounting rails 28 are positioned perpendicular tomounting rails 24, 26 to form the substantially rectangular mountingframe 12. A central air distribution conduit 27 is positioned centrallyin the mounting frame 12 to supply the aeration elements 15 with anairflow, in the manner to be described below. The aeration elements 15are each coupled to the central air distribution conduit 27 via asuitable coupling to enable air flow into the aeration elements 15 andsecured to the mounting rails 24, 26 with brackets 17. As shown in FIG.5B, mounting brackets 17 are secured, for example screwed, onto mountingrails 24, 26. When the aeration elements are position onto the mountingframe, as shown in FIG. 5C, brackets 17 engage around the aerationelements 15 proximate to opposite ends of the aeration elements 15, sothat the aeration elements 15 are thereby secured to the mounting rails24, 26 and a length of each aeration element 15 extends beyond therespective mounting rail 24, 26. By way of example, the bracket deviceof U.S. Pat. No. 9,81,480 to the same inventor as the presentapplication is referenced, the subject matter of which is incorporatedherein by reference. The central air distribution conduit 27 in turn isconnected to a further air distribution conduit 29 arrangedperpendicular to the central air distribution conduit 27 and extendingvertically upward to the bridge assembly 2, in particular, the walkway20, for connection to an air supply provided via a flexible air hose 52provided on the walkway 20. The air distribution conduit 29 extendsupwardly from the mounting frame 12 and between vertical guide rails 34,36 of the vertical guide rail system 19 described in greater detailbelow.

By way of example, the aeration elements 15 are shown as elongatedaeration strip elements having a substantially oval cross-section, withan elastomeric and flexible tubular membrane having air slits providedonly on a top surface of the aeration element when the membrane isplaced around the aeration element, and an air inlet with a threadedconnection to connection the aeration element to a distribution conduitthat serves for the supply of gas or air. In this type of aerationelement, the support member of the aeration element is made up of arigid, hard plastic material having a corrugated, hollow profiled andwith corrugated outer surfaces, such that a plurality of grooves isformed between the ridges of the corrugated surfaces, both on the innerand outer surfaces of the support member. However, as noted above, themounting frame assembly can be used with tubular or disc-shapeddiffusors/aeration elements, which are known in the relevant art, withthe same effect as strip diffusors with an oval cross section.

As noted above, the mounting frame assembly is designed to providebuoyancy when the aeration elements are in place on the mounting frame12. The frame components themselves are preferably made of a lightweightmetal, such as stainless steel, although other suitable lightweightmaterials could be used to the same effect. The construction of theaeration elements 15, in particular, by their elongated design, whethertubular or flattened with an oval cross section, also provide buoyancyto the mounting frame assembly. (Reference is made to U.S. Pat. No.9,70,752 by the same inventor as the present invention, the subjectmatter of which is incorporated by reference, with regard to an exampleof the elongated, oval-cross sectional aeration elements that could beutilized with the mounting frame assembly). While the hold-down bracketor rod 37 assists in lowering the mounting frame 12 with the aerationelements 15 in place into the tank, positioning the mounting frame 12onto the floor of the tank, and maintaining the mounting frame 12 andaeration elements 15 in that position on the floor of the tank, thebuoyancy of the mounting frame 12 with the aeration elements 15 mayrequire adjustment of the air flow being fed into the aeration elementsto facilitate in lowering the mounting frame 12 into the water. Airflowpreferably is shut off for this particular aeration element and diffuserframe element, so that the aeration elements deflate to minimizebuoyancy. For example, the air supply can be stopped via a shut offvalve and air is then bled out of the air supply system via the aerationelements, allowing the mounting frame 12 to be more easily lowered intothe water.

Referring to FIGS. 6A-6B and 7, the mounting frame 12 with the aerationelements 15 in place can be removed manually out of the tank by securinga lift cable 100 to mounting frame 12, via a connection flange, forexample. The mounting frame 12 and aeration elements 15, therefore, canbe pulled manually out of the water tank 14, for example with the crane8 and lift cable 100, for maintenance or replacement of components.

The vertical guide rail system 19 is secured at an upper end via one ormore upper end fixing brackets 40 to the bridge 2 that extends from awall or walls 82 of the tank over the surface of the tank, extendingeither completely or partially between the walls of the tank. While thefigures show a circular tank, the water treatment system 10 also can beused for any other tank geometry, such as square or rectangular tanks.The air distribution line 22 is secured to a flexible hose 52, which inturn connects to one or more air supply conduits 54 running on theoutside of a bridge railing or is mounted beneath the walkway 20 of thebridge 2, for supplying air to the aeration elements 15 in the mountingframe 12.

As noted above, the water treatment system 10 includes the bridge 2, themounting frame assembly 6, the vertical guide rail assembly 19, alifting crane 8, and a transport device 58. The transport device, orcart, 58 can be a wheeled cart, shown by way of example as cart 58, formoving the mounting frame 12 and aeration elements 15 along the bridge 2and walkway 20, into position for deployment into the water tank ormoving the mounting frame 12 and aeration elements 15 off the bridge 2for repair or maintenance.

As best shown in FIGS. 3A-3B, the lifting and pivoting crane 8 includesa mounting base 102, a post 103, and a lifting and pivoting arm 104. Themounting base 102 is secured to the walkway 20 of the bridge 2. In thisconnection, the walkway 2 is provided with a plurality of mountingplates 90 that are secured to the surface of the walkway 2, eachmounting plate 90 having a plurality of through-holes 91 for securingthe mounting plate 102. The crane 8 preferably is positioned between twovertical guide rail assemblies 19, so that one crane 8 can service bothassemblies 19 by pivoting the crane's lifting and pivoting arm 104. Thepivoting and lifting arm 104 extend beyond an upper rail 64 of thebridge 2 at a height sufficient to allow the crane 8 to engage, lift,and pivot the mounting frame 12 onto the bridge, specifically, onto thetransport device 58, shown here as moveable cart or frame, positioned onthe walkway 20. The crane 8 includes a pulley line 100 for attachment toa flange or other element on the central air conduit 27 in the mountingframe 12.

After the mounting frame 12 has been removed from the water tank via thevertical guide system, 19, the crane 8, in a known manner, then isoperated to manually move the mounting frame 12 from a position disposedabove the water and perpendicular to the bridge 2 and walkway 20 intoposition onto the transfer cart 58, as shown in FIGS. 6A and 6B. Themounting frame 12 then can be released from the pulley line 100 of thecrane 8 and transported via the moveable cart 58 off the bridge 2 andwalkway 20 and onto the transfer station 22 to be removed from thebridge 2 (FIG. 15). Likewise, the mounting frame 12 and aerationelements 15 can be loaded onto the transfer cart 58 at the transferstation 22 and moved onto the bridge 2 and walkway 20 from the transferstation 22, so that the mounting frame 12 and aeration elements 15 canbe deployed into the tank, either initially or after servicing.

FIGS. 4A through 4B show further perspective and end views,respectively, of the water treatment system 10, including the bridge 2,the vertical guide rail system 19, the retrievable mounting frameassembly 6, and the cart 58. As shown in FIGS. 4A and 4B, the mountingframe assembly 6 may further include a stabilizing arm 101 secured atone end to the control arm 25 and at an opposite end to the frame 12 tofacilitate in raising and lowering the frame 12 and aeration elements 15into and out of the water in a level manner.

FIG. 7 shows a view of the mounting frame 12 and crane 8, with themounting frame 12 in place on a moveable transport device 58, such as awheeled cart or frame. As can be seen also from FIG. 13, the transfercart 58 is generally formed as a lightweight but sturdy rectangularsteel or metal frame with upper rails 95, lower rails 97, and verticalrails 99 extending between and connecting the upper rails 95 and lowerrails 97. The transfer cart 58 includes wheels or castors 59 positionedon the lower rails 97 to facilitate movement of the cart 58 in guidetracks 21 formed in the walkway 20 of the bridge 2. The cart 58 isdimensioned to conform to the width of the bridge 2 and walkway 20 andhas a height that enables the mounting frame 12 to be positioned on thecart 58 such that the mounting frame 12 with the aeration elements 15have adequate clearance over the upper rail 64 of the bridge 2 andwalkway 20 during transport of the transfer cart 58 along the walkway20.

While the crane 8 was described above as mounted and fixed to the bridge2, as shown in FIGS. 9A through 13D, a further embodiment of the crane 8contemplates that the crane 8 is more readily transferable betweenmounting plates 90 fixed to the walkway 20. The crane 8 is similar infeatures to the crane 8 described above, except in this embodiment, themounting base 102 can be fixed instead to a transfer trolley 300. Thetransfer trolley 300 has a substantially rectangular base plate 302 andwheels and/or castors 304 positioned on and mounted via mountingbrackets 310 to opposite sides of the base plate 302. The mounting base102 is secured to the base plate 302 of the transfer trolley 300 via aplurality of bolts, for example. Further bolts 308 secure the base plate302 of the transfer trolley 300 to the walkway 20 by engaging throughthe through-holes 91 provided in the mounting plates 90. In operation,and as illustrated in FIGS. 8A and 8B, the crane 8 is secured to thetransfer trolley 300, and the transfer trolley 300 secured to a mountingplate 90 on the walkway 20 proximate to at least one vertical guide railassembly 19. FIGS. 9A and 9B illustrate transfer of the crane 8 via thetransfer trolley 300 between mounting plates 90 on the walkway 2. Oncethe transfer trolley 300 and therefore the crane 8 are secured to themounting plates 90 on the walkway 2, the crane 8 is then ready to beoperated to live and or lower the frame 12 and aeration elements 14 fordeployment on the vertical guide rail system (FIGS. 10A and 10B) or fortransfer of the frame 12 and aeration elements 15 onto and off thetransfer cart 58 (FIGS. 11A-11B). As shown in FIGS. 12D and 12E, forexample, the wheels engage and move in the guide tracks 21 on thewalkway 20 which are also used by the transfer cart 58. When it isnecessary to transfer the crane 8 to a different location on the bridge2, the bolts 306 can be loosened/removed and the transfer trolley 300manually relocated along the guide tracks 21 for securing to a furthermounting plate 90 on the walkway 20.

As noted above, the water treatment system 10 includes at least onetransfer station 22, as shown in FIG. 14. The transfer station 22 ispositioned at one or both ends of the bridge 2 and walkway 20 andincludes a platform 400 for receiving the transfer cart 58 with theframe assembly positioned thereon. The transfer station 22 is positionedto extend above and over the wall of the tank 14 so that the platform400 is disposed outside of the tank 14. When a frame 12 with aerationelements is to be deployed in the tank 14, the transfer cart 58 is movedto the transfer station by an operator and the frame 12 with aerationelements 15 can be loaded onto the cart 58 via a mobile crane orforklift at the transfer station 22 and then transported from thetransfer station 22 along the walkway 20 of the bridge 2 into positionfor deployment. Likewise, when a frame 12 with aeration elements 15 mustbe removed from the tank 14, the transfer cart 58 with the frame 12 withaeration elements 15 is moved along the length of the bridge 2 to thetransfer station 22 where it can be picked up with the forklift ormobile crane and be serviced on the grounds outside the tank, or broughtto a maintenance area or workshop of the waste water treatment plant.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

What is claimed is:
 1. A method for aerating water in a treatment basin,comprising: positioning at least one bridge above an upper surface ofthe water in the basin, the at least one bridge comprising a walkwayextending from a first sidewall portion of the basin to a secondsidewall portion of the basin; providing at least one retrievablemounting frame assembly, comprising a frame; a plurality of aerationelements; a plurality of mounting brackets to secure the aerationelements to the frame; and a first air distribution conduit coupled tothe aeration elements for supplying an air flow to the aerationelements; securing at least one guide rail assembly to the bridge,wherein the at least one guide rail assembly extends from the at leastone bridge to a floor of the basin; transporting the at least onemounting frame assembly on a transport device to a selected position onthe walkway proximate the at least one guide rail assembly; securing atleast one transfer crane to the walkway proximate the at least one guiderail assembly; transferring the at least one mounting frame assemblyfrom the transport device for connection to the at least one guide railassembly using the at least one transfer crane; connecting the at leastone mounting frame assembly to the at least one guide rail assembly toprovide a supply of air to the first air distribution conduit; movingthe retrievable mounting frame assembly from a first position above theupper surface of the water to a second position below the water; andinitiating a flow of air to the first air distribution conduit.
 2. Themethod of claim 1, wherein the walkway includes parallel guide tracksextending along a length of the walkway.
 3. The method of claim 2,wherein the at least one transport device includes wheels and/or castorsconfigured to engage in the guide tracks.
 4. The method of claim 1,wherein the at least one transport device has a width that correspondsto a width of the at least one bridge.
 5. The method of claim 1, whereinthe at least one transfer crane includes a mounting base configured tobe secured to the walkway proximate to the at least one vertical guiderail assembly.
 6. The method of claim 1, wherein the at least onetransfer crane includes a mounting base.
 7. The method of claim 6,further comprising providing a transfer trolley with a base plate and aplurality of wheels and/or castors and securing the mounting base to thebase plate of the transfer trolley.
 8. The method of claim 7, whereinthe walkway comprises at least one crane mounting plate, and wherein thebase plate of the transfer trolley is configured to be secured to the atleast one mounting plate.
 9. The method of claim 7, wherein theplurality of wheels and/or castors are configured to engage in theparallel guide tracks.
 10. The method of claim 1, wherein the at leastone guide rail assembly comprises first and second parallel guide rails;a second air distribution conduit coupled to the first air distributionconduit; and a push-rod positioned between the guide rails and connectedto the retrievable mounting frame assembly.
 11. The method of claim 10,wherein the push-rod is configured to facilitate movement of themounting frame assembly along the guide rails between the first positionabove the upper surface of the water and the second position.